Buildings having flat roofs or roofs having only slight pitch are often provided with multi-ply roof constructions. A base sheet and several layers of roofing felt and insulation panels are superimposed to build up the ultimate roof. To seal and adhere the respective layers to the roof and to adjacent layers, a layer of liquid roofing composition (hereinafter "asphalt") typically including a mixture of tar, pitch, and bituminous components is interposed between each layer. The means and methods of applying the asphalt to successive layers heretofore employed have generally been slow, labor intensive, and inefficient.
One method used to apply asphalt is to dip a mop into a bucket or wheelbarrow containing heated asphalt and to spread the asphalt using the mop. It is not uncommon for such mops when loaded with asphalt to weigh on the order of 85 lbs. or more. Moreover, the fumes and heat of the asphalt require that the user hold the mop handle relatively far away from the mop head, thus increasing the effective weight by leverage. An alternative method is to pour quantities of the asphalt onto the roof and to use the mop to spread the asphalt. In either method, great physical effort is required and the rate at which the asphalt may be applied is low.
To reduce the drawbacks of the mop method, various apparatus have been developed for dispensing strips of hot asphalt of substantially uniform thickness. These devices typically include a wheeled tank for holding hot asphalt. A slot or series of openings are formed along the bottom of the tank. The asphalt is gravity fed through the openings. The rate at which the asphalt is dispensed may be controlled by a valve.
One such device, the MINI MOPPER.TM. coater from Garlock Inc. of Texas, employs a rotary bar valve having a hollow, cylindrical tube with opposed transverse holes formed therethrough. When the tube is rotated into an "open" position, asphalt from the tank is able to flow through the holes. When the tube is rotated into a "closed" position, the ends of the holes are closed off by adjacent walls. A third, transverse hole is formed between each of the first two holes. When the tank is in the closed position, the third hole serves as a drain for asphalt trapped in the tube. The tube is provided with two or three series of dispensing holes which allow the device to dispense asphalt strips of different widths. The apparatus discussed above, while a significant improvement over application by mopping, suffers several significant drawbacks in practice.
In order to properly apply a multi-ply roof, different widths of materials and different widths of overlap must be used. The strips of asphalt applied prior to laying these materials should be of widths corresponding to the width of the material or the desired overlap. For example, insulation panels are typically 2 feet by 4 feet, 3 feet by 4 feet, 4 feet by 4 feet, or 4 feet by 8 feet. Ideally, the panels are applied by applying a strip of asphalt which is 28 inches, 38 inches, or 48 inches wide, respectively, and laying the panels end to end onto the asphalt while it is still hot liquid. Further, at the edges of a roof it may be necessary to break the insulation panels into smaller widths to achieve a proper fit. The above described device cannot be efficiently used to apply all such full and partial panels because it has only two or three dispensing widths. A similar problem is encountered at the cants and tie-ins of a roof. At these locations, felt layers are laid in successively wider, overlapping widths. Typically, a 9 inch wide felt is applied, followed by an 18 inch wide felt, followed by a 27 inch wide felt, followed by a 36 inch wide felt. Asphalt strips of appropriate widths must be applied for each layer. Again, the devices discussed above are unable to apply all such widths. Where the dispensing apparatus cannot be employed, the asphalt must be applied by mop.
Another problem encountered with the above described device results from the use of a hollow tube for the bar valve. Notwithstanding the provision of the drain holes, in practice a substantial amount of asphalt trapped in the tube upon closing the valve cools and hardens before it can escape through the drain holes.
Another problem experienced with dispensing apparatus as described above is that they are difficult to maneuver. Moreover, these apparatus are generally formed from steel, making them very heavy.
Another portion of a roof which requires the application of hot asphalt is the cant along each edge. The cant is a wedge shaped strip typically angled at about 45.degree. which provides a slope between a raised lip along the roof perimeter and the roof. Conventionally, asphalt is applied to the cant by the mop method. The dispensing devices as discussed above do not provide for dispensing of asphalt onto the cant. One device designed to avoid mopping of asphalt onto the cant uses a wide roller which passes through a pool of asphalt. A strip of roofing felt is manually drawn over the roller which transfers asphalt onto the felt. The felt is then laid onto the roof. This process is messy and difficult to employ as the felt tends to twist and buckle, particularly if wind is present.
Thus, there exists a need for a convenient and cost effective apparatus for applying strips of hot asphalt to a roof. Moreover, there exists a need for such an apparatus which may be used to selectively apply strips of hot asphalt of different widths. There exists a need for a mobile hot asphalt dispenser which is more easily maneuverable. Further there exists a need for an apparatus and a method for applying hot asphalt from a mobile asphalt dispenser onto a cant of a roof. Additionally, there is a need for a means for reducing or eliminating the tendency of asphalt in a rotary bar valve to cool and harden before draining therefrom when the bar valve is placed in a closed position.